Heretofore efforts have been made to extract the potential heat energy from the sewage scum for heating purposes. Laboratory studies have shown that the scum is mainly grease having a potential energy of approximately 6000 BTU's per gallon, approximately the same as number six fuel oil.
One of the biggest obstacles in using the scum was the separation out from the grease of floating debris in the form of rocks, sticks, cardboard, plastic items, sand and so forth.
Heretofore apparatus has been known and used for the treatment of fluid waste products and sewage. Examples are found in the following U.S. Pats:
______________________________________ NUMBER DATE ______________________________________ 739,049 1903 3,909,410 1975 3,946,679 1976 3,475,178 1969 2,022,069 1935 2,379,754 1945 3,936,378 1976 ______________________________________
The foregoing were found in Patent Office Class 210, subclasses 67, 71, 72, 77, 81 and 403.